A fifth seasonal flu vaccine gained federal approval Thursday, further boosting the record levels of doses available for the upcoming influenza season.

The Food and Drug Administration said it approvedFluLaval in part by relying on safety data from Canada, where the vaccine has been available since 2001.

The vaccine is made by Id Biomedical Corp., a Canadian company purchased by the British pharmaceutical company GlaxoSmithKline PLC in 2005.

The Centers for Disease Control and Prevention estimate there will be about 115 million doses of vaccine for the 2006-07 flu season. GlaxoSmithKline hopes to combine stocks of FluLaval with its Fluarix vaccine, approved in 2005, and provide roughly 25 million to 27 million of those doses, a company spokeswoman said.

FluLaval is for use in adults only. It has not been tested in children or pregnant women.

The FDA-approved version contains thimerosal, a preservative made with a derivative of the toxic metal mercury. Glaxo plans to develop a thimerosal-reduced or thimerosal-free version that could be tested on children, the FDA said.

In 2004, production problems at one manufacturer caused severe shortages of flu shots.